An exhaust gas system for an engine is generally provided with a catalyst converter for purifying specified components contained in exhaust gas. As such a catalyst converter is widely used a three-way catalyst converter for, with respect to specified three components contained in the exhaust gas, oxidizing carbon oxide (CO) and unburned hydrocarbon (HC) and reducing nitride oxide (NOx), so as to convert the components into carbon dioxide (CO2), water vapor (H2O), and nitrogen (N2), respectively.
A catalyst included in the three-way catalyst converter is degraded in function at low temperatures. Therefore, the catalyst is unsatisfactorily burned unless the temperature of the catalyst is increased on an early stage at the time of cold starting, thereby raising a problem that the exhaust gas containing the specified three components, described above, therein in large quantities cannot be purified.
In the meantime, a hybrid vehicle becomes commercially practical, which is provided with an engine to be actuated by combustion energy of fuel and a motor to be actuated by electric energy as power sources during traveling of the vehicle, wherein an automatic transmission (including a power split mechanism) is interposed between the power sources and drive wheels. The above-described hybrid vehicle travels by independently using the engine and the motor according to, for example, an operational state, to thus reduce a fuel consumption or an exhaust gas quantity while maintaining a predetermined traveling performance. Specifically, there are a plurality of operational modes in different operational states of the engine and the motor: for example, an engine traveling mode, in which the vehicle travels by using only the engine as the power source; a motor traveling mode, in which the vehicle travels by using only the motor as the power source (while stopping the engine); an engine-motor traveling mode, in which the vehicle travels by using both of the engine and the motor as the power sources; and the like. These modes are designed to be automatically switched according to predetermined mode switching conditions expressed by, for example, a power source map using the operational states such as a vehicular speed (or a power source speed) and an acceleration operational amount as parameters. In other words, even if the vehicle travels, the engine may be intermittently operated.
Besides, there is a hybrid vehicle called a series type, that is, an electric automobile with an engine generator in which drive wheels are rotated by only a motor whereas an engine is actuated as a power supply source to a motor via the generator. In addition, there is a hybrid vehicle called a parallel type, in which wheels are directly driven by both of an engine and a motor, can travel while the motor assists power of the engine and electrically charges a battery as a generator.
Japanese Patent Laying-Open No. 2006-132394 discloses an exhaust gas purifier for a series type hybrid vehicle capable of efficiently purifying exhaust gas with certainty while suppressing an increase in cost. The exhaust gas purifier for the series type hybrid vehicle provided with a generator to be driven by an internal combustion engine, a battery to be electrically charged via an inverter by an output from the generator, and a motor receiving electric power from the battery via the inverter, is characterized by including exhaust gas purifying means disposed on an exhaust gas channel in the internal combustion engine and temperature increasing means for increasing the temperature of the exhaust gas purifying means upon the electric power supply from the battery via the inverter during stoppage of the internal combustion engine. Moreover, the exhaust gas purifier is characterized in that the exhaust gas purifying means is constituted of an oxidizing catalyst disposed on a front stage whereas a filter disposed on a rear stage for collecting particulate matters contained in the exhaust gas. Additionally, the exhaust gas purifier is characterized in that the filter is made of cordierite, and further, that the temperature increasing means is a heater disposed around the filter, for generating heat upon the electric power supply.
With the exhaust gas purifier for the series type hybrid vehicle, the exhaust gas purifier disposed on the exhaust gas channel in the internal combustion engine for the series type hybrid vehicle is increased in temperature by supplying the electric power to the temperature increasing means from the battery via the inverter during the stoppage of the internal combustion engine. Moreover, a so-called continuous regeneration type filter is used as the exhaust gas purifier, whereby hydrocarbon (HC) and carbon oxide (CO) contained in the exhaust gas are converted into carbon dioxide (CO2) and water (H2O), respectively, with the oxidizing catalyst disposed on the front stage, and nitrogen oxide (NO) contained in NOx is efficiently converted into nitrogen dioxide (NO2), thereby temporarily increasing an NO2 concentration whereas collecting PMs by the filter disposed on the rear stage, so that the PMs are burned with NO2 produced on the front stage. Additionally, when the filter is made of cordierite without any electrification, the heater is disposed around the cordierite filter. The electric power is supplied to the heater so as to allow the heater to generate heat, thereby increasing the temperature of the cordierite filter.
Meanwhile, performance of an electronic part such as a thyristor or a power transistor to be mounted on the hybrid vehicle is remarkably enhanced, and accordingly, a heat generation amount from the electronic part (i.e., a heat generating element) becomes larger. In the meantime, in, for example, a hybrid vehicle mounting an induction motor and a DC battery thereon (including an electric automobile or a fuel cell vehicle), an inverter converts power so as to supply the power from the DC battery to the induction motor. A heat generation amount of the electronic part such as the inverter is also increased according to an increase in rated output of the induction motor, thereby requiring sufficient cooling measures.
For the vehicle, the electronic part is demanded to be reduced in size and thickness, in particular. Even on such a demand, the importance of a cooler for speedily radiating a large generated heat to the outside becomes higher in order to keep stability of operation. A heat sink, an air-cooled fan, a heat pipe, and a water-cooled unit are used singly or in combination for cooling the aforementioned electronic part. Among them, a water-cooled unit is used in the case of markedly large heat generation.
In this manner, an electronic part such as an IPM (abbreviating an Intelligent Power Module) or an IGBT (abbreviating an Insulated Gate Bipolar Transistor) mounted on a PCU (abbreviating a Power Control Unit) is cooled (hereinafter, electronic parts to be required to be cooled may be referred to as power modules).
That is to say, such a power module is thermally exchanged between the power module and a liquid refrigerant (i.e., coolant), and then, the liquid refrigerant is thermally exchanged between air and the same in a radiator. Finally, the heat of the power module is wasted.
However, even in the Japanese Patent Laying-open No. 2006-132394 stated above, the electric power is merely supplied to the heater via the inverter, to increase the temperature of the filter, but the heat generated in the power module of the inverter cannot be effectively utilized.